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Vintage Amateur and Military Radio Amateur/military receivers and transmitters, morse, and any other related vintage comms equipment.

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Old 8th Dec 2017, 11:21 am   #1
IK0MOZ Mario
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Default Spy Set SSTR-1

I am starting to build a new home made replica of the american clandestine radio SSTR-1. I look for some inside pictures. I choose for the TX type the B version. If someone is interested to the same work, glad to share the esperience.
73 de mario
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Old 8th Dec 2017, 3:49 pm   #2
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Default Re: Spy Set SSTR-1

I suggest you try Google.

I found this very easily: http://militaryradio.com/spyradio/sstr1.html which has inside photos.
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Old 8th Dec 2017, 5:41 pm   #3
IK0MOZ Mario
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Default Re: Spy Set SSTR-1

TNX dear GMB, I started the replica following the P. McCollum site indications, but unfortunately some details it is not clear (Like the coils and 6L6 supports are secured to the front panel ?). mario
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Old 8th Dec 2017, 6:21 pm   #4
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Default Re: Spy Set SSTR-1

I have the "D" version of xmtr. It has the same mounting and the bracket is soldered to the back of the front panel.
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Old 8th Dec 2017, 8:41 pm   #5
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Default Re: Spy Set SSTR-1

Hello Mario,

There is a video on YouTube on the SSTR-1. It might be of some use to?

https://www.youtube.com/watch?v=3kLCvt9nKFs

73

Roger/G3VKM
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Old 8th Dec 2017, 11:14 pm   #6
IK0MOZ Mario
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Default Re: Spy Set SSTR-1

Many TNX Bruce (wanderfull call M0 SOE). Immagined because no screws on the front panel. It is possible attach here some inside photos of your model C ?
Roger TNX for link, I already seen, but no usefull for my work. 73
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Old 8th Feb 2018, 4:39 pm   #7
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Default Re: Spy Set SSTR-1

Done, or quasi.....SST-1 completed and operative. In this moment is in use a 6V6 with plate voltage of 250 Vdc. Power 2-2.3 W. In this conditions already done several QSOs and contacted France (449) and Germany (439). I am assempling a 400 V PSU and then i will put in a 6L6 tube. Missing some knobs and external box
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Old 8th Feb 2018, 4:51 pm   #8
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Default Re: Spy Set SSTR-1

Nice work! I love home-made tank coils/ inductors. I'm also struck by the lettering on the black case. How did you do the white lettering? It looks totally fit for purpose.

What is a QSO?
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Old 8th Feb 2018, 5:15 pm   #9
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Default Re: Spy Set SSTR-1

Lovely!

You should be able to get at least 5 Watts of RF out of a 6V6 when it's working in Class-C at RF.

A 6L6 will give you 15 Watts of RF - at risk of overdriving the crystal!
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Old 8th Feb 2018, 9:45 pm   #10
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Default Re: Spy Set SSTR-1

Quote:
Originally Posted by astral highway View Post
What is a QSO?
In amateur radio it's a contact, other unrelated disciplines have other meanings of course: http://www.qsl.net/w5www/qcode.html
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Old 9th Feb 2018, 9:55 am   #11
IK0MOZ Mario
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Default Re: Spy Set SSTR-1

TNX for the comments. For the lettering very simple, I used a rubber characters kit made to homebuilt stamp. Manufacturer TRODAT type 6004 (4 mm). Unfortunately no found white ink for stamp and used a white pen to wet the letters so the result no very good.
About the power 5 W should be OK, I guess that my 6V6 is a little tired, so I will test other tubes. It is possible to get 5 W with 250 plate voltage or in any case I have to improve the voltage ? TNX to all - Mario
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Old 9th Feb 2018, 12:00 pm   #12
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Default Re: Spy Set SSTR-1

I would say Bella! Think that is correct in Italian.
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Old 9th Feb 2018, 6:16 pm   #13
astral highway
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Default Re: Spy Set SSTR-1

Quote:
Originally Posted by IK0MOZ Mario View Post
T It is possible to get 5 W with 250 plate voltage or in any case I have to improve the voltage ?
5.5W is given as the absolute maximum rating for the tube. If you ran it at 350V on the anode and 34mA, you would over-drive it 100%.

If you ran it at this anode current and 250V, you would still be over-driving it by around 50%.

Seems unwise to push it to 5W CW.
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Old 9th Feb 2018, 6:31 pm   #14
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Default Re: Spy Set SSTR-1

Max anode dissipation is given as 12 watts.

Lawrence.
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Old 9th Feb 2018, 10:38 pm   #15
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Default Re: Spy Set SSTR-1

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Max anode dissipation is given as 12 watts.
Your source, please?

Here in the trustworthy Radio Museum, it clearly states at the bottom of the page, in 'Absolute Maximum Operating Conditions ... Pout, 5.5W'

http://www.r-type.org/exhib/aaa0015.htm

If you multiply the maximum anode current by the maximum voltage, you get close to your 12W, but that doesn't mean the valve can tolerate it. It is 100% overdriven if we do this.

Many power devices can be operated in pulse mode without exceeding these conditions, but that isn't realistic for CW. Triode-connected in one of its historic roles, as a TV vertical deflection amplifier --i,e, in pulse mode, with over 1KV on the anode-- it could dissipate 9W.

(Can anyone refresh my memory on the *historic* (not current) frequency, hence period, of the vertical deflection circuit pulses, contemporary with this valve?) I'm thinking in the range tens of uS to sub 1mS...

But if we actually look at the detail on the downloadable PDF for 'typical operation', when it is actually doing the useful work that we value, the valve is derated to 4.5W out with 250V on the anode.
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Last edited by astral highway; 9th Feb 2018 at 11:00 pm.
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Old 9th Feb 2018, 10:48 pm   #16
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Default Re: Spy Set SSTR-1

https://frank.pocnet.net/sheets/127/6/6V6.pdf

Max anode dissipation and Pout are not the same thing.

The clue is in the word "dissipation" ie getting rid of heat.
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Old 10th Feb 2018, 12:25 am   #17
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Default Re: Spy Set SSTR-1

Quote:
Originally Posted by astral highway View Post
Quote:
Originally Posted by ms660 View Post
Max anode dissipation is given as 12 watts.
Your source, please?
Sorry I'm late....It's all in here, including the Pa max power curve:

https://frank.pocnet.net/sheets/084/6/6V6GT.pdf

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Old 10th Feb 2018, 2:11 pm   #18
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Default Re: Spy Set SSTR-1

It's the difference between audio use and RF PA operation. For CW the valve will be in Class C with nominally 66% efficiency. For 12W anode dissipation this can give an RF output of up to 24W.
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Old 10th Feb 2018, 6:48 pm   #19
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Default Re: Spy Set SSTR-1

That’s interesting , Keith - and it’s great to hear your expertise to validate what is theoretically possible ...

but we don’t know it is running in class C!

Sticking to the verifiable facts in ‘Notes from a user’ (link in post #2) , these clearly state that when the set was in use, the output was up to 10W with the valve horizontally mounted and immersed in motor oil as a coolant! I love this ingenuity!

This is significant, because it suggests that even to get 10W out, anode dissipation would rise above the limit of with this tube of convection in air, (12W) which suggests a class of RF operation with just natural air (not forced-air) cooling that was not particularly efficient, definitely nowhere close to 66%.

It also describes an ancillary RF amplifier for specific use with an RCA 815 twin beam power valve, comfy at 25W out, suggesting that this was the ‘natural’ design for covering the miles with this suitcase unit.

I wonder could we see the circuit diagram?
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Last edited by astral highway; 10th Feb 2018 at 7:16 pm. Reason: Adding historic detail
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Old 10th Feb 2018, 6:54 pm   #20
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Originally Posted by astral highway View Post
I wonder could we see the circuit diagram?
See the links in post #2.
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